Student Members: Dianny Melgar, Colby Fletcher, Nikka Macaraeg, Gus Schumacher
Faculty Advisors: Dr. Scott Hamel
Project Mentor: Brian A. O’Dowd, PE
Description:
With the Alaska Railroad (ARRC)’s projected growth on the south end, improvements need to be made to its infrastructure throughout its corridor south of Whittier. One such key piece of infrastructure is the bridge at ARRC milepost 14.5 that crosses Snow River just north of Seward. The existing bridge currently spans 716’ and consists of (4)-150’ thru-truss pans with open decks, (3)-29’ I-Beam spans with ballast decks, and (1)-29’ I-Beam span with an open deck. To accommodate future growth, and to combat flood surges associated with Jökulhlaups (glacial lake outburst) and seasonal weather, adjustments to the existing track layout and low chord elevation of the superstructures need to occur. Improvements are to ensure that both current and future operations continue to be resilient and sustainable for years to come. An alternatives analysis was conducted by a previous Capstone group in 2020. The final report of this project can be found here: https://tinyurl.com/mtjjz8b8
ARRC has determined that the low chord elevation of the structure needs to be raised approximately 4.0-feet. To accommodate the new elevation of the superstructure, the track will need to be raised on either end of the bridge and laid out in a manner that reduces curves and spirals. The aforementioned track raise and reduction of curves affects an existing multi-plate grade separation structure at ARRC milepost 14.3 where the track goes under the Seward Highway. As a result of the required track raise, the multi-plate structure will have to be removed and it is likely that a highway overpass will need to be constructed over the track.
To ensure that the infrastructure where the railroad crosses Snow River is both resilient and sustainable, the following items may need to occur in addition to the above:
• Scour protection to include riprap armoring and/or river training.
• Removal and replacement of the south approach spans.
• Rehabilitation or replacement of the north approach span.
• Installation of new bulkheads at either end of the bridge.
Project elements that may be inclusive to this work are, but not limited to, the following: interagency negotiations (i.e.: coordinating with the AKDOT&PF), civil site improvements (e.g.: grading, drainage, parking etc.), constructability (to include environmental impacts), railroad track design, superstructure raise and substructure improvements (geotechnical/structural), rough-order of magnitude construction cost estimates, and traffic design (evaluating and incorporating AKDOT&PF design recommendations).
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